The present invention relates to a mounting device for sensors and pick-ups according to the preamble of claim 1.
Without the comprehensive application of sensors and pick-ups it would be impossible to solve the problems of modern technology. In the broader sense, sensors are virtually the eyes and ears of any electric control device, basically even of any automatic technical operation.
Frequently, however, problems are encountered in connection with such technical sensors, for example optical systems such as light barriers, inductive or capacitive pick-ups, ultrasonic sensors and their correcting receivers, and the like, because their sensitive zones get increasingly contaminated by dirt or covered up by undesirable layers, for example when sensors are installed in, or even intended to observe, a dirty environment.
The preferred embodiment of the invention relates to a mounting device for optical dust detecting means, for example in the form of a luminous diode/phototransistor combination used in a vacuum cleaner. This application will, therefore, be regarded hereafter in greater detail, although it is understood that the invention is by no means restricted to it.
It has been known in connection with vacuum cleaners, for example, to arrange at least one light transmitter and a coacting light receiver adjacent the channel which is passed by the dirt and dust particles drawn in, so that the detected dirt level is indicated, or the power of the electric motor driving the blower is changed over, in response to the quantity of dirt and dust particles (still) flowing through the suction channel which is then compared with a given threshold value (DE-OS No. 34 31 164). It has been further known in this connection to arrange the optical dust detecting means in a separate housing which is either fixed on the suction channel of the vacuum cleaner or mounted between the suction nozzle and the suction pipe and which is switched on as required by a separate minimum pressure governor responding to a given minimum pressure in the suction pipe (published European Patent Application No. 0 231 419).
All these sensors are, however, connected with the problem that the effectiveness of their sensitive zones may get impaired or even fully lost because these areas get clogged, i.e. covered up, fully or in part, by dust settling from the environment or, especially in the case of vacuum cleaners, by dusts or the like, flowing past such areas.
Due to the fact that it is difficult or practically impossible to produce optical dust detecting means projecting into a suction channel with absolutely smooth surfaces and/or inner faces, since at least the sensitive area of the respective sensor or optical sensor or receiver must project through, or be arranged flush with, the wall of the channel, there is always the risk that dust particles or lint may be caught in the transition area, retain and collect other dusts and solid particles and, finally, gradually cover up the sensitive area. The same may happen in the case of light barriers or ultrasonic pick-ups installed in machines or other systems when they are exposed to the risk of contaminations settling gradually on their sensitive areas from the surrounding air.
While manual cleaning of the sensor surfaces is not excluded, it is not always possible in practice. Applied to vacuum cleaners, this may be the case, for example, when the optical dust detecting means are arranged on either side of a long narrow channel, i.e. at a location which is not, or not readily, accessible by the fingers or some device. In addition, it is not to be expected that such a cleaning procedure will be actually performed in all cases.
Now, it is the object of the present invention to provide a mounting device for sensors of any type, and especially for optical dust detecting means of a vacuum cleaner, which is designed in such a manner that cleaning is effected automatically.